Formulating and Answering High-Impact Causal Questions in Physiologic Childbirth Science: Concepts and Assumptions

Maternal Morbidity Predicted by an Intersectional Social Determinants of Health Phenotype: A Secondary Analysis of the NuMoM2b Dataset

Maternal race, ethnicity and socio-economic position are known to be associated with increased risk for a range of poor pregnancy outcomes, including maternal morbidity and mortality. Previously, researchers seeking to identify the contributing factors focused on maternal behaviors and pregnancy complications. Less understood is the contribution of the social determinants of health (SDoH) in observed differences by race/ethnicity in these key outcomes. In this secondary analysis of the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be (nuMoM2b) dataset, latent mixture modeling was used to construct groups of healthy, nulliparous participants with a non-anomalous fetus in a cephalic presentation having a trial of labor (N = 5763) based on SDoH variables. The primary outcome was a composite score of postpartum maternal morbidity. A postpartum maternal morbidity event was experienced by 350 individuals (6.1%). Latent class analysis using SDoH variables revealed six groups of participants, with postpartum maternal morbidity rates ranging from 8.7% to 4.5% across groups (p < 0.001). Two SDoH groups had the highest odds for maternal morbidity. These higher-risk groups were comprised of participants with the lowest income and highest stress and those who had lived in the USA for the shortest periods of time. SDoH phenotype predicted MM outcomes and identified two important, yet distinct groups of pregnant people who were the most likely have a maternal morbidity event.

Association between first and second stage of labour duration and mode of delivery: A population-based cohort study

BACKGROUND

Active first stage of labour duration can widely vary between women. However, the nature of the relationship between the active first stage and second stage of labour duration is sparsely studied.

OBJECTIVES

To determine whether active first stage of labour duration (i) influences second stage of labour duration; and (ii) is associated with mode of delivery.

METHODS

A population-based cohort study of 13,379 women primiparous women, with spontaneous start in Stockholm-Gotland Region, Sweden, between 2008 and 2014. Duration of the active first stage of labour was examined in relation to second-stage duration using univariate and multivariable quantile regressions, with the first quartile (first stage duration) as the reference. Nonlinearity of associations was tested by restricted cubic splines. Association between active first-stage duration with mode of delivery was estimated using a multinomial logistic regression based on adjusted odds ratios.

RESULTS

Longer active first stage of labour duration was linearly associated with longer second stage of labour duration until approximately 12 h of active first stage of labour duration. After 12 h, a non-linear trend is seen, demonstrated by a plateau in the second-stage duration. In addition, longer active first stage of labour duration was associated with increased occurrence of operative vaginal delivery (adjusted odds ratio 3.36, 95% confidence interval [CI] 2.89, 3.89) and caesarean delivery (adjusted odds ratio 4.75, 95% CI 3.85, 5.80).

CONCLUSIONS

Among primiparous women with spontaneous onset of labour, longer active first stage of labour duration was associated with both longer second stage of labour duration and higher odds of operative delivery. This study contributes with findings, which may inform future discussions regarding how to properly account for second-stage duration, with applications in obstetric and perinatal epidemiology.

Challenges in the Triage Care of Low-Risk Laboring Patients: A Comparison of 2 Models of Practice

Triage and the timing of admission of low-risk pregnant women can affect the use of augmentation, epidural, and cesarean. The purpose of this analysis was to explore these outcomes in a community hospital by the type of provider staffing triage. This was a retrospective cohort study of low-risk nulliparous women with a term, vertex fetus laboring in a community hospital. Bivariate and multivariable statistics evaluated associations between triage provider type and labor and birth outcomes. Patients in this sample (N = 335) were predominantly White (89.5%), with private insurance (77.0%), and married (71.0%) with no significant differences in these characteristics by triage provider type. Patients admitted by midwives had lower odds of oxytocin augmentation (adjusted odds ratio [aOR] = 0.50, 95% confidence interval [CI] = 0.29-0.87), epidural (aOR = 0.29, 95% CI = 0.12-0.69), and cesarean birth (aOR = 0.308, 95% CI = 0.14-0.67), compared with those triaged by physicians after controlling for patient characteristics and triage timing. This study provides additional context to midwives as labor triage providers for healthy, low-risk pregnant individuals; however, challenges persisted with measurement. More research is needed on the specific components of care during labor that support low-risk patients to avoid medical interventions and poor outcomes.

Metabolic Pathways Associated With Term Labor Induction Course in African American Women

OBJECTIVES

The purpose of this study was to evaluate differences in the metabolic pathways activated in late-pregnancy serum samples among African American women who went on to have term (≥37 weeks) labor induction requiring high total oxytocin doses to complete first-stage labor compared to those in similar women with low-oxytocin labor inductions.

STUDY DESIGN

Case-control study (N = 27 women with labor induction with successful cervical ripening: 13 requiring the highest total doses of synthetic oxytocin to progress from 4- to 10-cm cervical dilation and 14 requiring the lowest total doses) with groups balanced on parity and gestational age. Serum samples obtained between 24 and 30 weeks' gestation were analyzed using ultra-high-resolution metabolomics. Differentially expressed metabolites between high-oxytocin induction cases and low-oxytocin induction comparison subjects were evaluated using linear regression with xmsPANDA. Metabolic pathways analysis was conducted using Mummichog Version 2.0, with discriminating metabolites annotated using xMSannotator Version 1.3.

RESULTS

Labor processes were similar by group with the exception that cases received over 6 times more oxytocin between 4- and 10-cm cervical dilation than comparison women. Induction requiring high total doses of synthetic oxytocin was associated with late-pregnancy serum levels of metabolites from the linoleate and fatty acid activation pathways in term, African American women.

CONCLUSION

Serum levels of several lipid metabolites predicted more complicated labor induction involving higher doses of synthetic oxytocin to complete first-stage labor. Further investigation in larger, more diverse cohorts of women is needed to identify potential targets to prevent failed labor induction.

Metabolomic Pathways Predicting Labor Dystocia by Maternal Body Mass Index

Objectives  The purpose of this study was to evaluate the metabolic pathways activated in the serum of African-American women during late pregnancy that predicted term labor dystocia. Study Design  Matched case-control study ( n  = 97; 48 cases of term labor dystocia and 49 normal labor progression controls) with selection based on body mass index (BMI) at hospital admission and maternal age. Late pregnancy serum samples were analyzed using ultra-high-resolution metabolomics. Differentially expressed metabolic features and pathways between cases experiencing term labor dystocia and normal labor controls were evaluated in the total sample, among women who were obese at the time of labor (BMI ≥ 30 kg/m2), and among women who were not obese. Results  Labor dystocia was predicted by different metabolic pathways in late pregnancy serum among obese (androgen/estrogen biosynthesis) versus nonobese African-American women (fatty acid activation, steroid hormone biosynthesis, bile acid biosynthesis, glycosphingolipid metabolism). After adjusting for maternal BMI and age in the total sample, labor dystocia was predicted by tryptophan metabolic pathways in addition to C21 steroid hormone, glycosphingolipid, and androgen/estrogen metabolism. Conclusion  Metabolic pathways consistent with lipotoxicity, steroid hormone production, and tryptophan metabolism in late pregnancy serum were significantly associated with term labor dystocia in African-American women.

The ARRIVE Trial: Interpretation from an Epidemiologic Perspective

The findings of the ARRIVE trial (A Randomized Trial of Induction Versus Expectant Management) were recently published. This multisite randomized trial was designed to provide evidence regarding whether labor induction or expectant management is associated with increased adverse perinatal outcomes and risk of cesarean birth among healthy nulliparous women at term. The trial reported that the primary outcome, a composite of adverse neonatal outcomes, was not significantly different between the 2 groups; the principal secondary outcome, cesarean birth, was significantly more common among women whose pregnancy was expectantly managed than among women whose labor was induced at 39 weeks. These results have the potential to change existing practice. Several aspects of the study design may influence its potential internal and external validity and should be considered in order to make sound causal inferences from this trial, which will in turn affect how its findings are translated to practice. Although chance and confounding are of minimal concern, given the sample size and randomization used in the study, selection bias may be a concern. Studies are vulnerable to selection bias when the sample population differs from eligible nonparticipants, including in randomized controlled trials. External validity is defined as the extent to which the study population and setting are representative of the larger source population the study intends to represent. External validity may be limited given the characteristics of the women enrolled in the ARRIVE trial and the practice settings where the study was conducted. This brief report provides concrete suggestions for further analyses that could help solidify conclusions from the trial, and for further research questions that will continue advancement toward answering this complex question of how best to manage labor and birth decisions at full term among low-risk women.